1. Field of the Invention
This invention relates to electrical current regulation. More specifically, it concerns an integrated circuit that is temperature-compensated for generation of a uniform reference current.
2. Description of the Prior Art
It has been difficult to provide temperature independent current sources from an integrated circuit because of large positive temperature coefficients of high value diffused/ion implanted resistors. Such resistors heat up during operation and the current varies with temperature. To overcome this difficulty, an external resistor has been used with an internal reference such as a bandgap regulator or a zener diode. This approach provides a low temperature coefficient and a good absolute value, but requires an extra pin and component.
Another approach has been to use low temperature coefficient resistors on an integrated circuit chip instead of an external resistor. This approach has several disadvantages. The lowest temperature coefficient of diffused or ion-implanted resistors that are obtainable in a practical process is too high for current references. Low temperature coefficient resistors are low in value per area unit and thus, large areas are required for typical current values in the micro-ampere to milli-ampere range. High concentration diffusions used for low value resistors are not controlled for absolute value.
It is desirable to use integrated circuits including diffused resistors for providing a current source, but until this time, the problem of uniform current generation over a wide range of temperatures remained to be solved.